Diet and Asthma

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Summary of practice points

 Level of evidence
Food allergens are uncommon triggers for asthma in any age group; diet should not be restricted unnecessarily. II
Treatment of proven food allergies involves avoidance of foods known to cause symptoms. [√]
Skin prick tests or RAST will be positive for foods that cause IgE-mediated food allergies. [√]
There is no medical foundation for the widely held view that dairy products increase mucus secretions. [√]
Weight reduction in overweight or obese people with asthma may help to reduce asthma symptoms III
Exclusive breastfeeding for the first 6 months of life should be encouraged for all infants. III
Breastfeeding can protect against allergic rhinitis, wheezing, asthma and atopy in children. [√]

People with asthma are often interested in the effect that diet may have on their symptoms. While food allergens are uncommon triggers for asthma, health professionals need to be aware of the issues and myths surrounding diet and asthma: many patients with chronic diseases seek alternative advice from other practitioners, including those with little experience and often no scientific basis for their recommendations. Patients should be particularly wary of any advice that claims that a change in diet can cure asthma and eliminate the need for medication.

Food as a trigger for asthma

Food allergy

  • IgE-mediated reaction to a food protein in a patient with a food protein allergy can result in bronchoconstriction.
  • The most common foods that may cause IgE-mediated food allergy are peanuts, tree nuts, fish, shellfish, milk, eggs, wheat and soy.
  • Most children grow out of their allergy to milk, eggs, wheat and soy, but allergies to peanuts, tree nuts, fish and shellfish can to be lifelong.1
  • The only dietary treatment currently available for proven food allergy is complete avoidance of the food protein.
  • The presence of asthma is a risk factor for serious food allergic reactions.
  • Food allergy must be confirmed by appropriate tests done by an allergy/immunology specialist.

For more detailed information on food allergy and asthma, go to Asthma and allergy.

Food chemical intolerance

  • Some food chemicals have been reported to trigger symptoms of asthma.
  • There is currently no evidence that avoidance of food additives has any routine role in asthma management.
  • Investigation for food chemical intolerance must be conducted in a specialised unit and involves investigation with double-blind, placebo-controlled challenges.
Food trigger Evidence
Sulphur dioxides
Used for bleaching, improving and stabilizing food ingredients		 Considered the most reactive food additive; Ingestion or inhalation can cause bronchoconstriction; may affect up to 5-10% of people with asthma.
Monosodium glutamate (MSG)
Widely used as a flavour enhancer		 The existence of MSG-induced asthma has not been firmly established.
Tartrazine
Synthetic yellow dye used for colouring foods, drugs and cosmetics		 No firm conclusions regarding the effects of tartrazine exclusion in asthma.
Acetyl salicylic acid
ASA and several other types of salicylate derivatives occur naturally in some foods		 There is no evidence to recommend that people with aspirin sensitivity should avoid naturally occurring dietary salicylates.
Practice points
  • Food allergens are uncommon triggers for asthma in any age group; diet should not be restricted unnecessarily. (II)
  • Treatment of proven food allergies involves avoidance of foods known to cause symptoms. [√]
  • Skin prick tests or RAST will be positive for foods that cause IgE-mediated food allergies.  [√]
  • There is no medical foundation for the widely held view that dairy products increase mucus secretions.  [√]

Food as a potential treatment for asthma

Studies are ongoing into the potential role of dietary supplements for the treatment of asthma. There is currently no conclusive evidence for using dietary supplements, including probiotics or antioxidants, in the treatment of asthma.

Food treatment Evidence
Omega-3 polyunsaturated fatty acids Little evidence to recommend that people with asthma supplement or modify their dietary intake of marine omega-3 fatty acids in order to improve their asthma.6
Antioxidant vitamins C and E Evidence insufficient to recommend a specific role for vitamins C or E in the treatment of asthma.7, 8
Magnesium Meta-analysis found that magnesium supplementation may be beneficial in children with mild-to-moderate asthma; further research required before it can be recommended.9
Selenium Currently insufficient evidence that selenium supplementation is of benefit in asthma.10
Sodium Currently insufficient evidence that a low sodium diet will be of benefit in asthma.11

Practice tips

  • People with asthma should follow a diet appropriate for general good health, including consumption of fresh fruits and vegetables, lean meats and fish, wholegrain breads and cereals, dairy products and oils low in omega-6 fatty acids such as olive oil or canola oil.
  • People with asthma on high-dose corticosteroids should use calcium supplementation.
  • When food choices are restricted, the advice of a dietitian should be sought to ensure that the dietary intake continues to meet nutrient and energy needs.

Weight loss in the obese patient

Epidemiological studies have shown an association between increasing body mass index (BMI) and increased prevalence of diagnosed or reported asthma in both adults and children.12,13,14,15  Weight reduction in both obese and morbidly obese asthmatics has been associated with improved symptom scores and reduced medication requirements.16,17 Health professionals should consider discussing weight loss in overweight and obese patients with asthma.

Practice point
Weight reduction in overweight or obese people with asthma may help to reduce asthma symptoms. (III)

Infant feeding

Exclusive breastfeeding for the first 6 months of life should be encouraged for all infants. In the general population and in atopic families, breastfeeding can protect against allergic rhinitis, wheezing, asthma and atopy in children.18

If exclusive breastfeeding is not possible, supplementation with cows' milk formula is recommended. There is no evidence to support a soy based formula over a cows' milk formula in infants at risk of developing asthma.19  A hydrolysed formula may be indicated for infants at high risk of developing asthma.20,21

Practice points
  • Exclusive breastfeeding for the first 6 months of life should be encouraged for all infants. (III)
  • Breastfeeding can protect against allergic rhinitis, wheezing, asthma and atopy in children. (V)